1. Field
A tack-free artificial nail surface formed using odorless monomers.
2. Background
Free Radical Polymerization is usually carried out in vacuum or inert atmosphere like argon or nitrogen. If carried out in atmosphere, oxygen present in air, acts as a radical scavenger and inhibits polymerization. The resulting polymer may or may not achieve the molecular weight to yield desired properties.
Some monomers like ethyl methacrylate (“EMA”) or methyl methacrylate (“MMA”) are exceptions because growing EMA radicals prefer reacting with another EMA monomer instead of reacting with oxygen or kMM>>>>>kMMO2 where k=rate of propagation of polymer, MM=reaction of growing polymer radical with another monomer and MO2=reaction of growing polymer radical with oxygen. The above equation reveals that the growing polymer radicals are very selective and almost exclusively react with another EMA monomer. Thus, in spite of EMA emitting a strong odor, this system is consistently used in the artificial nail industry.
In case of odorless monomers such as methoxyethoxy ethyl methacrylate (“MOEOEMA”) and tetrahydrofurfuryl methacrylate (“THFMA”), the growing polymer radical is not very selective and it reacts with atmospheric oxygen almost as well as with another monomer. In this case the equation happens to be kMM>kMMO2. The growing polymer near the surface reacts with atmospheric oxygen resulting in a tacky surface. Thus, polymerization results in a high molecular weight polymer formed under a low molecular weight polymer, which is the tacky surface. The manicurist must then remove this tacky layer from the surface to reveal a hard plastic coating.
The resultant tacky layer is undesirable because the manicurist has to put a very thick coat on the nail bed for nail enhancement. The thickness of the finished product gives it a very plastic look and not the natural look of EMA. The manicurist also incorrectly assumes that the bottom layers are not fully cured. Thus, this tacky layer prevents these odorless systems from capturing a significant share of the artificial nail market.
Efforts have been made to eliminate the tacky layer. In other systems, adding wax to the system has helped eliminate the tacky surface. The wax rises to the surface and shields the growing polymer from oxygen and polymerization proceeds to completion. The wax then flakes off. For some unknown reason, the addition of wax to the system disclosed in the present application does not eliminate the tacky surface. Efforts to eliminate the tacky surface have also included carrying out polymerization in a nitrogen or argon atmosphere. Although this procedure has been successful, it is not a practical solution. A further option is immersion of the polymerizing nails in warm water (which excludes oxygen and speeds the cure). This once popular method is no longer considered good practice because it creates a substantial risk of skin sensitization due to traces of uncured monomer in the water. Significant positive attributes of these systems, like non-crystallizing and non-lifting phenomena, are overlooked in the face of this tackiness. Tackiness has become a big hurdle to commercial success of these odorless systems.
Thus, an odorless artificial nail system that results in a non-tacky nail surface remains desirable.